I see 40g, 60g, and 80g or more insulation on jackets, but I don't know what weather each is meant for. Being too warm is my main concern, since being cold can just be fixed by layering. For example there is a 40g insulated jacket I really like, but I ride in SoCal where it's 50ish degrees F right now... Is 40g too warm for me? And what temps is 40g intended for?